by Steve Hampton
When assessing injuries to a spill, we typically seek to estimate,
using scientific methods, the actual number of birds impacted by the
event. For a variety of reasons, the number of birds collected (live
and dead) on the beach may be only a small fraction of the total number
impacted. The majority of the birds are never found. This page illustrates
some of the reasons why. It is also important to note that a relatively
small amount of oil on a bird (e.g., the size of a nickel) may result
in death (see photo at right, with small amounts of oil on the breast).
Like a hole in a wetsuit, the oil destroys the feathers' ability to
insulate the bird, thus allowing cold ocean water to spread against
the bird's skin. Birds typically die of hypothermia.
Scavenging
Coyotes, gulls, ravens, and other predators and carrion feeders
may quickly prey on live beached birds or remove carcasses from the
beach. OSPR studies have demonstrated that most birds disappear within
24 hours. This carcass is only hours old.
Removal or Burial by the Public
Beach-goers encountering dead birds may bury them or put them in
garbage cans. This bird, shown here exumed from the grave next to
its grave marker, was buried by the public within 20 minutes of its
death. This is despite the fact that it was early in the morning
and there were only four people on the beach.
At-Sea Loss
Experiments have shown that dead birds may float at sea for up to
two weeks. However, wind and currents may carry such birds such that
they never make landfall. This bird was apparently attacked and swallowed,
then regurgitated. It was found floating at sea.
Departure from the Area
Large birds are sometimes able to travel long distances before succumbing
to the effects of oiling. These birds may travel well outside the
spill response zone and beyond the notice of responders. In some
cases, we have documented birds travelling 60 miles from the spill
site within two days. This Brown Pelican, heavily oiled on the belly,
was found at Port San Luis during the Torch/Platform Irene oil spill.
This location is approximately 40 miles from the spill site.
Beach Transit
The general assumption that birds come ashore and stay on the beach
is not always valid. Common Murres, a seabird not known for walking
great distances, have been found many hundreds of yards inland during
oil spills. Sixteen sets of fresh murre tracks were counted on this
0.75 mile-long beach, all heading straight out of the water and up
into the dunes. However, no birds were found despite intensive searching.
Unsearched Areas
Significant stretches of the coastline often go unsearched because
they are inaccessible. While it is sometimes assumed that such reflective
coastlines are non-depositional, a recent OSPR study revealed that
birds do wash up on such beaches if rocky pockets exist.
Search Efficiency
OSPR studies have shown that finding beachcast birds is not so easy.
In fact, search efficiency plummets with small, dark-bodied birds.
In this photo, on a beach free of wrack and other material, note
the footprints (far left) of the observer who missed this carcass
(far right). Beachcast birds are easily overlooked on cobble shorelines
strewn with kelp and debris.
Re-Wash
Some beaches have sand at low tide, but are swept clean at high
tide. A recent OSPR study shows that some birds are scavenged on
land, swept back into the sea, sink, and are further scavenged by
crabs.
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